In the construction or mining industries, large machines carry wheels or chains with spaced mounting blocks which carry contact tools or mining bits. Each block has a cylindrical recess to receive the mounting shank of a bit and the cutting or tip portion of the bit projects from the block.
It is generally desirable to have these bits rotate in the blocks to reduce the wear on the bit and equalize the wear around the bit. Reducing the wear of the bit extends the life of the bit and thus, reduces the down time of the machines necessary to replace worn bits. Also, providing a bit which wears evenly provides a self-sharpening action which further extends the life of the bit and reduces the down time of the machines.
U.S. Pat. No. 3,833,264 discloses a mining bit which has a plurality of protuberances, or a straight or spiral fm, or a head having a plurality of flat faces with a complimentarily shaped tip. The protuberances, fms or side edges of the flat faces provide turning means serving to strike the surface contacted by the bit to rotate the bit within the mounting block. However, the protuberances, fins or three straight edged sides of the bit formed accordingly wear rather rapidly necessitating frequent replacement and hence, increased down time of the machine.